The technology of the present disclosure relates generally to combining power from electrically isolated power paths for powering remote units in distributed antenna systems (DASs).
Wireless communication is rapidly growing, with ever-increasing demands for high-speed mobile data communication. As an example, local area wireless services (e.g., so-called “wireless fidelity” or “WiFi” systems) and wide area wireless services are being deployed in many different types of areas (e.g., coffee shops, airports, libraries, etc.). Distributed communications or antenna systems communicate with wireless devices called “clients,” “client devices,” or “wireless client devices,” which must reside within the wireless range or “cell coverage area” in order to communicate with an access point device. Distributed antenna systems are particularly useful to be deployed inside buildings or other indoor environments where client devices may not otherwise be able to effectively receive radio-frequency (RF) signals from a source, such as a base station for example. Example applications where distributed antenna systems can be used to provide or enhance coverage for wireless services include public safety, cellular telephony, wireless local access networks (LANs), location tracking, and medical telemetry inside buildings and over campuses.
One approach to deploying a distributed antenna system involves the use of RF antenna coverage areas, also referred to as “antenna coverage areas.” Antenna coverage areas can be formed by remotely distributed antenna units, also referred to as remote units (RUs). The remote units each contain or are configured to couple to one or more antennas configured to support the desired frequency(ies) or polarization to provide the antenna coverage areas. Antenna coverage areas can have a radius in the range from a few meters up to twenty meters as an example. Combining a number of remote units creates an array of antenna coverage areas. Because the antenna coverage areas each cover small areas, there typically may be only a few users (clients) per antenna coverage area. This arrangement generates a uniform high quality signal enabling high throughput supporting the required capacity for the wireless system users.
As an example, FIG. 1 illustrates distribution of communications services to coverage areas 100(1)-100(N) of a DAS 102, wherein ‘N’ is the number of coverage areas. These communications services can include cellular services, wireless services such as RFID tracking, Wireless Fidelity (WiFi), local area network (LAN), WLAN, and combinations thereof, as examples. The coverage areas 100(1)-100(N) may be remotely located. In this regard, the remote coverage areas 100(1)-100(N) are created by and centered on remote units 104(1)-104(N) connected to a central unit 106 (e.g., a head-end controller or head-end unit). The central unit 106 may be communicatively coupled to a base station 108. If the DAS 102 is a broadband DAS, the central unit 106 receives downlink communications signals 110D in multiple frequency bands for different communications services from the base station 108 to be distributed to the remote units 104(1)-104(N). The remote units 104(1)-104(N) are configured to receive downlink communications signals 110D from the central unit 106 over a communications medium 112 to be distributed as downlink communications signals 110D to the respective coverage areas 100(1)-100(N) of the remote units 104(1)-104(N). Each remote unit 104(1)-104(N) may include an RF transmitter/receiver (not shown) and a respective antenna 114(1)-114(N) operably connected to the RF transmitter/receiver to wirelessly distribute the communications services to client devices 116 within their respective coverage areas 100(1)-100(N). The remote units 104(1)-104(N) are also configured to receive uplink communications signals 110U in multiple frequency bands over antennas 114(1)-114(N) from the client devices 116 in their respective coverage areas 100(1)-100(N) to be distributed over the communications medium 112 to the central unit 106.
Power is provided from one or more power sources to the remote units 104(1)-104(N) in the DAS 102 to provide power for the power-consuming components in the remote units 104(1)-104(N). For example, the remote units 104(1)-104(N) may receive power P over long wire electrical conductor pairs 118 (“wire pair 118”) provided in the communications medium 112 from one or more power sources 120 (“power source 120”). For example, the power source 130 may be remote to the remote units 104(1)-104(N) and provided at the central unit 106 or other location in the DAS 102. The power source 120 may be either an alternative current (AC) or direct current (DC) power supply. Each wire pair 118 may carry a limited amount of current or voltage, which may be dictated by safety regulations or by physical properties of the wire pairs 118, such as their diameter and length. However, in some cases, one or more of the remote units 104(1)-104(N) may require more power than can be carried by a single wire pair 118. For example, NEC (National Electrical Code) Class 2 directives may limit the power that can be provided by a single power supply to 100 VA (Volt-Ampere).
One solution to deliver more power to the remote units 104(1)-104(N) is to connect multiple wire pairs 118 from multiple power output ports 122(1)-122(X) to each remote unit 104(1)-104(N). In this arrangement, each wire pair 118 provides power up to its limited power level. However, the power provided by all wire pairs 118 can be combined in parallel to provide a greater combined power to a remote unit 104(1)-104(N). However, the voltages at the end of each wire pair 118 may be different due to different voltage drop on the wires, differences in the adjustment of the power supply 120, and/or differences in components' tolerances in the power output ports 122(1)-122(X) of the power supply 120. If the voltages at the end of each wire pair 118 are not equal, this will cause the power supply 120 to distribute different current and thus different power P on power output ports 122(1)-122(X) to a remote unit 104(1)-104(N). In such case, some power output ports 122(1)-122(X) will deliver lower power while the other power output ports 122(1)-122(X) will deliver higher power. If power P pulled by the power supply 120 reaches the limit allowed by safety regulations or capabilities for a given power output port(s) 122(1)-122(X), the power supply 120 may shut down thereby interrupting power P to the remote units 104(1)-104(N).
No admission is made that any reference cited herein constitutes prior art. Applicant expressly reserves the right to challenge the accuracy and pertinency of any cited documents.